At last, Abraham leaves Egypt with Sarah and goes back to the Promised Land. St. Ambrose tells us that Sarah represents virtue, so that, even though Abram lived in Egypt, he remained faithful to virtue and did not depart from her side.
Once in the Promised Land, he must fight for water and he manages to do it amicably, not clinging to his rights but finding a peaceful solution with the Lot's herdsmen. And God who sees all remembers Abram and visits him with a second promise:
Lift up your eyes, and look from the place where you are, northward and southward and eastward and westward; for all the land which you see, I will give to you and to your descendants forever. I will make your descendants as the dust of the earth; so that if one can count the dust of the earth, your descendants also can be counted. Arise, walk through the length and the breadth of the land, for I will give it to you." So Abram moved his tent, and came and dwelt by the oaks of Mamre, which are at Hebron; and there he built an altar to the LORD.
Abram then prefers the spiritual blessings to the goods of this world. He pins his hope on God's promise instead of a well. He does not expect the Earth to feed him, rather he believes that God will provide.
How is his situation different from ours? How are we true followers of Abram when we contracept and refuse to have more children because "the Earth will not provide?"